How much CFM for a 360?

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MOhorsePAR

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Hello everyone, O:) Long time reader, new member.

I purchased a motor from a buddy of mine a while back with less than 500 miles on a new build. It is a 360 +.030 with approx 9.8:1 compression, Comp XE-274 cam, air gap intake, Hooker headers. It currently has a 600 CFM Edelbrock that runs quite nice on the street.

However the question I have is this -
Is that enough carb for the motor / cam combo? I expect to the car to see mostly street with an occasional pass at the track.
Your thoughts on which carb to run and why,,,,,

Thanks!
Steve
 
I would think that a Holley 3310/750 or a 780 Avenger would work good for you. I would think that the 600 is a little to small once you get into the higher rpm's.

Jack
 
If u can borrow a 750 to 850 for a friend to try u will have your answer. IMO u will feel the differance. but for every day cruising I would use the 600.
 
MOhorsePAR said:
Hello everyone, O:) Long time reader, new member.

I purchased a motor from a buddy of mine a while back with less than 500 miles on a new build. It is a 360 +.030 with approx 9.8:1 compression, Comp XE-274 cam, air gap intake, Hooker headers. It currently has a 600 CFM Edelbrock that runs quite nice on the street.

However the question I have is this -
Is that enough carb for the motor / cam combo? I expect to the car to see mostly street with an occasional pass at the track.
Your thoughts on which carb to run and why,,,,,

Thanks!
Steve
Click to expand...

That setup isn't to far off of my setup. 600 is ok for the street but you will not be as much fun for racing. I actually started out with a 750 Edel and I hated it so much I could never get it tuned in right with the engine. I tried a 600 a buddy had and it tuned up nicely but it had nowhere near the balls it did with the 750 when the 750 actually wanted to run right. I ended up getting a 650 mighty demon recommended by by a few others from this site and been very happy since.
 
don't forget cfm is just the air flow that can pass through the carb. So you can run a 750 carb but you might have to lean it out if you engine cannot suck sufficient air through it to get a good air fuel mixture with the jets that it has. search the net for a carb cfm calculator. It should get you pointed in the right direction
 
Im running a 750 Demon on a stock 360. Its a little much but still vac. secondaries. I had to lean it down a bit like others have said. I used to run a 750 Double Pumper on the 340 in my Cuda, didn't like it nearly as much.
 
not overkill BUT they were jetted correctly and probably didn't inhale 800cfm
 
I found that a Hollley 650 with mach. seconderys is a great match with a 360.

I may eveing know a person that has a new one with the box 4-sale...
 
650 is my vote considering your build. Running a 650 mighty demon myself. This was the advice I had gotten. I'm running 340 10.1 with 292 cam. Seems pretty good so far in the garage
 
Just posted 3 carbs for sale in the for sale forum...any of them would probably work well for you. Take a look and shoot me a PM if your interested.
 
I ran 12.95 at 104 with my 360 and a 600 Holly Double pumper.
I borrowed a buddy's 750 Edelbrock performer after that run and ran a 13.02. 30 minutes later another 13.0 something. I put my 600DP back on and it went right back to 12.9. I ran it with the 600 until I sold the car.
 
dodgefreak8 said:
not overkill BUT they were jetted correctly and probably didn't inhale 800cfm
Click to expand...

Thats right. But man,is a properly set up TQ ever a kick in the pants! I currently have a 650 cfm eddie on my 318. I did have an 850 cfm TQ. WAY BETTER ACCELERATION WITH THE TQ!! Better mileage too. Just love that sound too!
 
DemonDave said:
The stock 360 4bbls came with an 800cfm Thermoquad from the factory... overkill?
Click to expand...


You can't compare a spread bore to a square bore when it comes to selecting carb size. The Thermoquad has small primaries, smaller than a 600 square bore and the secondaries never opened all the way on a stock vehicle. So the fact that the ultimate CFM was 800 is pretty much irrelevant.

I have had a 600 (Holley VS), 670 (Holley Street Avenger), 725(BG Road Demon) and 750 (Holley VS- 3310) on my 360.

The throttle response and mid range reponse was awsome with the 600. It did give up enough to the 725 and 750 to feel it in the butt dyno above 4000 rpm. However, the 750 and 725 didn't have nearly as good throttle response as the 600. As a matter of fact the 725 was horrible below 2000 rpm. If it was a decision between those three carbs I would say the 600 all the way for a primarily street driven vehicle.

The most recent carb is the 670 Street Avenger. This carb has to be the closest to a drop on an go carb I have ever tried. The throttle response is as good as the 600 and I feel no difference by the butt dyno with the 725 or 750. Plus the 670 is giving me 2.5 mpg more thean the 600 and 5 mpg more than the 725 or 750. The 670 is unique in that it is a square bore (all the throttle baldes are the same size) but the primary vernturi's are noticabley smaller than the secondaries. This has to be the reason that it has such good throttle response.

Just like cams, it's better to error on the small side. A slightly small carb will give up much less on the top end than the bigger carb gives up on low mid range throttle reponse.

FWIW, my car with the 600 carb has run a very traction limited 13.7 @102 quarter with a 2.2 60' time. If I was to sort out my traction issues I could run low 13's with the 600 carb. I don't have any numbers on the others.

IMHO, I would not invest money in a new carb until get a chance to try some other sizes. The 600 is not going to cost you much, maybe a .1 or two in the 1/4 but you could definately be giving up a lot of throttle reponse an mid range driveablity not to mention the gas mileage.
 
i run a 625 cfm carter on my 360, it suits me just fine.

and it doesnt have to be the fastest thing on the track for bracket racing, just consistent.

so if you can get a 600 - 650 to tune right, go that way. IMHO.
 
Thanks guys for all the great input! O:)

Due to the fact that my current Edelbrock 600 doesn't have a choke setup on it (previous owner took it out), I have been leaning toward a 650 Speed Demon. Starting up that XE-274 cammed 360 in cold weather without a choke is a pain!

Any thoughts on the 650 Speed Demon vs the 670 Street Avenger?

Steve
 
My vote would be for a spread-bore manifold and a nice, big early ThermoQuad. Not the later TQ with the non-adjustable idle jets.
 
The 725 Road Demon I mentioned earlier was a nice looking carb and had some decent features an equivalent holley doesn't BUT. I had all kinds of trouble getting the engine to run smooth below 2000 rpm, spent the entire summer dicking with it. My biggest disapointment was in dealing with Barry Grant, their tech support stinks and when I decided what I really needed was a 650 Speed Demon (the 725 Road Demon is a 750 Speed Demon with a choke kit and slightly differnent jeting) and the only difference was the venturi size in the main body and the main jets I figured I would just buy a main body. BG refused to sell me a main body uder any secumstances. Just becuase of the poor customer service I can't recomend them any more.

Big difference between the Speed Demon 650 and 670 Street Avenger is price. The Speed Demons cost more and don't come with a choke or fuel line kit. The choke is an extra cost option. The Street Avenger comes complete including a fuel line kit and several secondary springs.
 
dcg333,
Thanks for the advice / experience. I think I'll take a good look at the 670 Street Avenger.

In reading up on the Speed Demon, I really liked some of the extra features that it has. However if it won't tune up and run right then the "extras" are of no use. :(

Thanks again to everyone for their input and help.

Steve
 
I noticed a big difference on the top end when I went from my Carter 625 AFB to my chokeless 850 cfm Thermoquad on my mildly built 340.

The bigger 2-1/4" TQ secondaries really kick in hard. The smaller AFB was soft on the top end.

Factory 360 HP motors came with the larger 1-1/2 primary TQ carbs which are called the 850cfm vs the 1-3/8 primary 800cfm carb.
 
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